1. Field of the Invention
The present invention relates to a method for making acylamides useful as protectants for cultivated plants against the phytotoxic action of herbicides. More particularly, the present invention relates to a method for making acylamides starting with the initial synthesis of an o-nitrophenoxyketone from an o-nitrophenol and a haloketone. The o-nitrophenoxyketone is then hydrogenated to produce a benzoxazine, which is thereafter acylated to form the desired acylamide.
2. Discussion of the Prior Art
Some of the acylamides which can be made in accordance with the method of the present invention are shown by Moser in U.S. Pat. No. 4,618,361. An acylhalide is reacted with an aromatic amine in the presence of an acid binding agent.
The term “acylamide” as used in the description of the present invention, includes compounds shown within the following formula: where R is a C(1-8) monovalent organo functional radical, R1 is a C(1-8) monovalent radical selected from the group consisting of, alkyl and alkoxyalkyl, and R2–R5 are C(1-8) monovalent radicals which can be the same or different, and are selected from the group consisting of hydrogen, alkyl and alkoxyalkyl.
Acylamides included within formula (1), can be synthesized by acylating a benzoxazine in an aromatic hydrocarbon solvent as shown by the following equation: where R–R5 are as previously defined and X is a halogen radical.
The formation of benzoxazines, such as 3,4-dihydro-3-methyl-2H-1,4-benzoxazine, can involve the initial synthesis and hydrogenation of a nitrophenoxyketone. For example, Strain et al. U.S. Pat. No. 2,381,935, shows the hydrogenation of o-nitrophenoxyacetone in an autoclave using a Raney nickel catalyst and methanol as a solvent to form a 3-methylbenzoxazine. However, a satisfactory synthesis for the o-nitrophenoxyacetone intermediate used in making the 3-methylbenzoxazine is not set forth by Strain et al.
Although a synthesis for the o-nitrophenoxyacetone intermediate used by Strain et al. is not reported, a procedure for making a phenoxyacetone is shown by H. Meerwein, Houben-Weill, Band 8—Saurstoffverindugen on page 57, by effecting reaction between phenol and monochloroacetone in the presence of potassium carbonate and sodium iodide. While a satisfactory yield of the phenoxyacetone is indicated, a strong solvent, such as a ketone, is used to solubilize the sodium iodide catalyst. Experience has shown that if sodium iodide is used as the catalyst to produce the phenoxyketone, further purification such as recrystallization is required. Otherwise catalyst poisoning can result during the hydrogenation step in the synthesis of the benzoxazine. As a consequence an excessive amount of waste can be generated.
In addition, as shown, for example, in Chemical Abstracts 102: 6171c and 103: 178335w (1985), and 106: 34646n and 106: 175898h (1987), phase transfer catalysts (PTC), such as tetrabutylammoniumbromide, have been used to facilitate the synthesis of ether related materials, such as acridine ethers, and aryloxy derivatives. Solvents such as toluene, aprotic solvents, or acetonitrile, have been found to be effective in the presence of K2CO3, or NaOH.
While some methods are shown to make acylamides of formula (1) by acylating a benzoxazine, improved procedures are constantly being evaluated for synthesizing benzoxazines, as well as precursors to benzoxazines, such as the corresponding nitroaryloxyketone, for example a nitrophenoxyacetone.